Odd hacked Ms Pac board problems

channelmanic

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FIXED: Odd hacked Ms Pac board problems

I have a hacked Ms Pac Man board on the bench. It's a single Pac Man board with Ms Pac ROMs on it and no daughter card.

It has a peculiar problem in that the text at the left side of both the top and bottom of the screen is duplicated. On the left side you see "1 up High" and on the right side you see the same thing.

At the bottom is "credit 0" on the left and "credit 0" on the right.

This doesn't affect the "Game Over" text on the screen or any of the game play BUT you can't see any score for player 2 because of the problem.

Have any of you seen a problem like this before?
 
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I have a hacked Ms Pac Man board on the bench. It's a single Pac Man board with Ms Pac ROMs on it and no daughter card.

It has a peculiar problem in that the text at the left side of both the top and bottom of the screen is duplicated. On the left side you see "1 up High" and on the right side you see the same thing.

At the bottom is "credit 0" on the left and "credit 0" on the right.

This doesn't affect the "Game Over" text on the screen or any of the game play BUT you can't see any score for player 2 because of the problem.

Have any of you seen a problem like this before?

Sounds like a bad VRAM addresser.
 
Thanks Mark,

I'll swap it out and see if that's the cure. If it is, I'll dig into it and see where the problem is.

RJ
 
Also check the back of the board for shorts. I would replace the socket for the vram addresser to rule that out.
 
Yup.... already checked for the shorts.

Will be checking the addresser tonight. Looks like a pretty simple mod to do a clean Ms Pac without the silly ribbon cable & card.
 
Yup.... already checked for the shorts.

Will be checking the addresser tonight. Looks like a pretty simple mod to do a clean Ms Pac without the silly ribbon cable & card.


It is an easy mod, just add two roms and something like 3 or 4 jumpers and cut 3-4 traces.
I wish I had a buck for every one of those I have unhacked.

Replace that socket first. The vram cards rarely go bad, its usually a connection issue or shorts on the backside from poor handling/storage.
 
Replace that socket first. The vram cards rarely go bad, its usually a connection issue or shorts on the backside from poor handling/storage.

If it were a socket problem, it would affect the main screen too, and not just the 2 lines at the top and bottom.
 
Pin 4 of the middle 74LS157 connects to pin 2 of the middle 74LS257 on both sides of the connector that plugs into the main board... Well, it was supposed to. It was broken and someone lumped solder on it to repair it and it didn't work.

One jumper later and the board is working well.

Thanks for the pointer Mark.
 
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